U.S. Pat. No. 5,033,271, assigned to the assignee hereof, discloses an apparatus for purification of refrigerant that includes a liquid refrigerant pump and hoses for selectively connecting the pump through a filter/dryer unit to the liquid and vapor ports of a refrigerant storage container. The pump circulates liquid refrigerant in a closed path from the liquid port of the storage container through the filter/dryer unit for removing water and other contaminates from the refrigerant, and then back to the vapor port of the refrigerant storage container. Operative condition of the filter/dryer unit is indicated by a differential pressure gauge connected across the filter dryer unit, and by a moisture indicator connected in series with the filter/dryer unit in the closed liquid refrigerant flow path. In the commercial embodiment of this device marketed by applicant's assignee, the device also includes a gauge as shown in U.S. Pat. No. 5,063,749, also assigned to the assignee hereof, for indicating pressure of air and other non-condensibles within the refrigerant storage container, and a manual valve for purging such non-condensibles from the purge port of the container.
Although the refrigerant purification apparatus so described has enjoyed commercial acceptance and success, further improvements are desirable. In particular, the sight glass moisture indicator employed in this apparatus, having an indication capability of 50 ppm for R-22 refrigerant and 80 ppm for R-134a refrigerant, cannot alone assure that the purified refrigerant meets current industry standards and guidelines in the range of 10 to 20 ppm. Consequently, there is a need for a compact, inexpensive and simple refrigerant purification apparatus and method of the type disclosed in the above-noted patents, but having improved capability for assuring that the purified refrigerant meets industry standards and guidelines. It is a general object of the present invention to provide such an apparatus and method. Another object of the present invention is to provide a method of employing the above-described device marketed by applicant's assignee and already in the field in such a way as to assure that purified refrigerant meets or exceeds current industry standards and guidelines.